Patent Application
20080017561
The invention is in general a trench filter device for severely reducing or eliminating hydrocarbon, liquid organic, and bacterial contamination of storm water discharging from a storm water system into the environment.
Storm water systems are well known and extremely common, typically consisting of large of numbers of storm drains and catch basins located in roadway curbs, within large paved areas such as parking lots, in drainage ditches, and the like. The storm drains allow the storm water to fall into catch basins. Conduits are connected to the catch basins to transport the storm water to discharge points where the storm water is returned to the environment. A storm water system is a vast network, and there are numerous recessed areas that act as sumps, either intentionally or unintentionally, where storm water remains resident within the system for extended periods of time, or at least until a subsequent storm event occurs. Such sumps occur in the pipes and conduits due to improper installation or shifting over time. Because the water may remain in these sumps for extended periods of time, and because the sumps will not necessarily be completely flushed upon subsequent storm events, the water retained in the sumps is prime for bacterial growth. This can result in an extremely high bacterial concentration in the discharge water when flushing of the storm system occurs. In other storm systems, surface ditches or trenches are utilized. These ditches and trenches are likewise susceptible to unacceptable bacterial growth in resident water trapped between storm events.
The invention solves the problem of excessive microbial ocntamination by providing an improved trench filter preferably comprising a combination filtration and anti-microbial medium that is positioned resident in the storm water pipes or ditches. The combination filtration and anti-microbial device is thus a resident filter and treatment means as well as a pass-though filter and treatment means. While the filter material may comprise many suitable materials capable of entrapping particulate matter, it is most preferable that the filter material acts as an effective means to adsorb hydrocarbon and liquid organic contaminants, as the presence of these components in discharge water is also undesirable. Many polypropylenes and polyesters, for example, are known to possess this adsorptive property.
The anti-microbial agent may be any of many suitable compositions, such as for example but not limited to an organosilane antimicrobial agent as disclosed in U.S. Pat. No. 5,954,869, the disclosure of which is incorporated herein by reference, which is suitably bonded, adhered, grafted, impregnated or otherwise joined to the filter material. The term anti-microbial is meant herein to include any compound, product, composition, article, etc., that reduces the growth and proliferation of microbial organisms, including but not limited to bacteria, viruses, protozoa, molds and the like. The anti-microbial agent is most preferably chosen from the group of such agents that are water-stable, such that the agent does not dissolve, leach or permeate into the storm water.
The trench filter 10 comprises an elongated cord or spine member 11 to which are attached a large number of filtration flaps 12, preferably formed by creating radially disposed slits 14 in sheet material attached to the spine member 11. The spine 11 may be formed of a flexible material, such as a rope or chain, or a rigid material, such as a PVC pipe. Means to the secure the device within a pipe or trench may also be provided. Water flowing through the pipes contacts the filtration flaps 12, such that particulate matter, hydrocarbons, organic liquids and other contaminants are captured prior to discharge of the water into the environment.
To improve this trench filter 10, an anti-microbial agent is incorporated in or on the filtration flaps 12. To further improve on the trench filter 10, radially extending rib or structural support members 13 of a rigid or semi-rigid composition are provided in the filtration flaps 12, preferably in the leading edges subject to water flow. Rib members 13 may be composed for example of PVC or similar material having suitable rigidity. The rib members 13 may extend completely across the spine member 11 so as to support two flaps 12. With this construction, the filtration flaps 12 will not be swept or oriented downstream by the force of the water, resulting in a generally axial orientation having smaller effective surface area and less contact with the water, but instead will remain disposed generally transversely or perpendicularly to the water flow direction in order to maximize the filtration and anti-microbial treatment effects by increasing the contact surface area and contact time of moving water.
Furthermore, as the trench filter 10 remains disposed within the pipe or trench, any water retained therein between storm events will remain in contact with some of the filtration flaps 12 containing the anti-microbial agents so as to eradicate or severely reduce the microbial concentration in the retained water. The trench filter 10 is left in the pipe until its effectiveness becomes diminished or until the filtration flaps 12 are filled with particulates, at which time it is replaced. In this manner, storm water remaining in the pipe is constantly treated such that the concentration of microbes is severely diminished or reduced to zero prior to the water being flushed from the system by the next storm event. In addition, the filter media removes by adsorption hydrocarbon and organic liquid contaminants in the sump water. The presence of the anti-microbial agent also prolongs the effective life of the filter media itself, since growth of bacteria, mold or other microbial species on the filter media that may interfere with the filtering effectiveness is precluded.
In certain instances it may be beneficial for the trench filter 10 to float, such as by providing a means to provide the spine 11 as a buoyant member, such that for higher water situations the spine 11 remains at or near the surface and the flap members 12 hang downwardly into the water. The spine 11 may comprise a sealed air chamber or may be made of material that is naturally buoyant. Alternatively, separate floatation means may be attached to the spine 11.
While the methodology and means has been described as a combination filtration and anti-microbial medium, it is also possible to accomplish the anti-microbial effect in the pipe utilizing a trench filter made of a non-filtering fabric or other matrix to carry the anti-microbial agents without filtration properties.
It is contemplated that equivalents and substitutions for certain elements set forth above may be obvious to those skilled in the art, and therefore the true scope and definition of the invention is to be as set forth in the following claims.
